Many industrial, commercial, and research processes require, for optimal results, that an object or material be maintained at a low temperature. For example, cryogenic preservation or maintenance at low temperature is a common means of insuring the molecular integrity of specimens and products. Substances that would degrade in a relatively short interval at higher temperatures can be stored with limited or no change for long durations at temperatures below the material freezing point. While frozen storage can be effective in decreasing the rate of sample degradation, in aqueous solutions and biological specimens, molecular activity does not cease until a temperature near −130° C. At temperatures above this point, there remains an opportunity for the specimen to re-order the solid structure, thereby creating changes in the specimen that may lead to a decrease in the integrity of the sample. Examples of this type of sample damage include, upon thawing, a decrease in viability of cryogenically stored cells, a reduction of enzymatic activity, and a decrease in the potency of pharmaceuticals.
The opportunity for deleterious changes in frozen specimens increases greatly under conditions where the sample experiences transient fluctuations in temperature such as may occur when stored materials are transferred from one cold storage system to another, or when held inside a storage system that undergoes temperature spikes, such as those introduced when a freezer door is opened for normal access, during intervals of power failure, or even during normal mechanical refrigeration temperature cycles over time.
Despite the need for prevention of temperature spikes and fluctuations in samples, there is often a need for extensive manipulation of samples outside of the normal frozen storage system. For example, cell vials may need to be re-organized, cataloged, or traced, requiring exposure to higher temperatures for time periods of several minutes to one-half of an hour or longer. Other requirements for extended manipulation time outside of freezer storage include preparation of samples for shipping or local transport; receiving, sorting, and storage of sample shipments; and packaging and labeling of frozen products.